This invention relates to a communication system, and more particularly, to a communication system that guarantees communication quality.
With broadband networks becoming widespread, there is an increasing demand for new services such as audio/video streaming and a business application running via a network in addition to conventional data communication services typified by downloading of a massive volume of data, Web browsing, and the like. In those new services, so-called communication quality such as in communication speed, delay of data, and jitter of the delay is required to achieve a predetermined level of quality in order to provide a service with stable quality.
In addition, due to the need for advancing diversification and globalization of data communication services, reducing costs necessary for data communication services, and early recovery of data communication services upon occurrence of a disaster, a distributed system configuration as illustrated in FIG. 15 is becoming mainstream as a method of arranging servers for providing the data communication services.
FIG. 15 is a block diagram illustrating a distributed system according to a conventional technology.
The distributed system according to the conventional technology includes a terminal 100, a terminal 101, an access network 1, a gateway 300, a network 2, and a server group 430.
The terminal 100 and the terminal 101 are connected to the access network 1 that is a communication network constituting communication means used by the terminal 100 and the terminal 101. The terminal 100 and the terminal 101 are each a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. Further, not only such two terminals as the terminal 100 and the terminal 101 but also a plurality of terminals having the same configuration are connected to the access network 1. The access network 1 is, for example, a mobile communication network or an optical communication network.
The access network 1 is connected to the network 2 externally via the gateway 300.
The gateway 300 is an interface between the access network 1 and the network 2. The gateway 300 is a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. The gateway 300 manages, for example, connection information and transfer information on a packet exchanged between the access network 1 and the network 2. In addition, the gateway 300 collects accounting charged for the terminal 100 and the terminal 101.
The network 2 is, for example, the Internet, a network built by a communications carrier, or a network built by a corporation or the like on its own.
The server group 430 is a cluster of servers arranged in a distributed manner. The server group 430 includes a control server 420 and a plurality of servers.
A server 410 and a server 411 are the servers arranged in the server group 430 in a distributed a manner. The server 410 and the server 411 are each a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. In addition, the server 410 and the server 411 each include an application program and a storage device, and provide a service to users of the terminals.
The control server 420 is a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. If the terminal 100 or the terminal 101 issues a request to use the service, the control server 420 decides on a connected server from within the server group 430 based on loaded conditions of the respective servers, and notifies the terminal that has issued the request to use the service of the connected server that has been decided on.
Hereinafter, a background technology is described by referring to FIG. 16 that illustrates a network configuration in a case of using a mobile communication network 3 as the access network 1.
FIG. 16 is a block diagram illustrating a distributed system according to the conventional technology which uses a mobile communication network.
The distributed system that uses the mobile communication network includes a mobile terminal 110, a mobile terminal 111, a base station 200, the mobile communication network 3, the gateway 300, the network 2, and the server group 430. The gateway 300, the network 2, and the server group 430 are the same as the gateway 300, the network 2, and the server group 430 illustrated in FIG. 15.
The mobile terminal 110 and the mobile terminal 111 are each a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. The mobile terminal 110 and the mobile terminal 111 are each connected to the mobile communication network 3 via the base station 200.
The base station 200 is a computer including a processor, an output device, an input device, a network interface, a memory, and an auxiliary storage device. The base station 200 converts packets transmitted from the mobile communication network 3 into radio signals, and transmits the radio signals to the mobile terminal 110 and the mobile terminal 111. In addition, the base station 200 converts radio signals transmitted from the mobile terminal 110 and the mobile terminal 111 into packets, and transmits the packets to the mobile communication network 3.
The mobile communication network 3 is connected to a plurality of base stations (in FIG. 16, the number of base stations is one) and the gateway 300, and transfers the packets between the base station 200 and the gateway 300.
For example, in the distributed system illustrated in FIG. 16, in a case where the mobile terminal 110 uses a new service, such as audio/video streaming or a business application running via the network 2, through the server 410, the mobile communication network 3 and the network 2 need to be controlled so that communications between the mobile terminal 110 and the server 410 may achieve predetermined quality.
Therefore, in the distributed system according to the conventional technology, RTP/RTCP and UDP protocols are implemented on the base station 200 as disclosed in, for example, WO 2005/027394 A1. By adding a technique disclosed in WO 2005/027394 A1, the base station 200 uses the RTP/RTCP and UDP protocols to analyze a signal transmitted between the server 410 (which is a fixed terminal in WO 2005/027394 A1 and the mobile terminal 110 and to measure communication quality between the base station 200 and the server 410, in other words, in the mobile communication network 3. The base station 200 uses the communication quality to calculate communication quality to be achieved between the base station 200 and the mobile terminal 110 and to adjust a transmission parameter of a wireless zone (between the base station 200 and the mobile terminal 110).
As conventional adjustment of a transmission parameter, there is exemplified priority control performed in the wireless zone as disclosed in, for example, JP 2007-053548 A.
FIG. 17 is an explanatory diagram illustrating a correspondence of priority indicators between the network and the wireless zone according to the conventional technology.
As illustrated in FIG. 17, in the system of JP 2007-053548 A, the base station 200 sets up a priority of a packet in the wireless zone according to priority indicators “A” through “D” in the network 1 and priority indicators “a” through “d” in the wireless zone, which are previously defined, and transmits the packet to the terminal via the wireless zone according to the priority indicator in the wireless zone. For example, the packet having the priority indicator “B” as a priority in the network 1 is given the priority indicator “b” as a priority in the wireless zone by the base station 200, and is transmitted to the terminal.